Investigation of the reproductive system in calanoid copepods: A new approach using 3D reconstructions from serial semi-thin cross-sections in Calanus glacialis and Metridia longa.

The structure of the female reproductive system of the calanoid copepods Calanus glacialis and Metridia longa from the White Sea was studied using light microscopy, scanning and transmission electron microscopy, as well as confocal laser scanning microscopy. For the first time, we applied also the method of 3D reconstructions from semi-thin cross-sections to visualize the general plan of the reproductive system in both species. The application of a combination of methods provided novel and detailed information on the genital structures and muscles located in the genital double-somite (GDS) as well as structures used for the reception and storage of spermatozoa, fertilization and release of eggs.

Seasonal dynamics and life histories of three sympatric species of in two Svalbard fjords.

Small copepods are the most diverse and numerous group in high-latitude zooplankton, yet our knowledge of important species remains poor because of the difficulties involved in correct species identification. In this study, we use a molecular method of identification, a species-specific polymerase chain reaction, to provide the first description of the seasonal dynamics and life histories of the important genus in two Svalbard fjords with contrasting environments. We conducted monthly investigations in the relatively warm and ice-free Adventfjorden, supplemented with seasonal samples from the colder, seasonally ice-covered Billefjorden.